Turboshaft engines are a type of gas turbine engine optimized for the production of shaft power rather than propulsive thrust. Turboshaft engines are often employed onboard watercraft, helicopters, and tanks, as well as utilized within auxiliary power units and industrial power generators. A turboshaft engine commonly includes an intake section, a compressor section, a combustion section, a gas turbine section, a power turbine section, and an exhaust section arranged in flow series. During operation, the intake section draws ambient airflow into the engine. The airflow is compressed within the compressor section and supplied to the combustion section wherein the airflow is mixed with fuel. The resulting fuel/air mixture is then ignited to produce combustive gases, which expand rapidly through the gas and power turbine sections to drive the rotation of the turbines contained therein. Rotation of the gas turbine or turbines drives further rotation of the compressor disk or disks, which are joined to the gas turbine by way of one or more shafts. Rotation of the power turbine (also referred to as the “free turbine” in platforms wherein the power turbine rotates independently of the gas turbine or turbines) drives the rotation of an output shaft, which serves as the rotary output of the turboshaft engine. Depending upon the particular platform in which the turboshaft engine is utilized, the output shaft may be coupled to a power generator and/or a propulsive element, such as the main rotor of a helicopter. After flowing through the power turbine section, the combustive gas flow is expelled from the engine through the exhaust section.
Ingestion of large quantities of sand, dust, ice, and other particulate matter into a gas turbine engine can cause various problems, such as accelerated compressor erosion, turbine blade glazing, bearing contamination, and cooling flow passage blockage, to list but a few examples. Turboshaft engines are especially prone to ingestion of sand and dust when utilized within contaminated environments and operated in close proximity to the ground, such as when deployed onboard a helicopter or tank operated in desert environment. For this reason, turboshaft engines are commonly equipped with Inlet Particle Separator (IPS) systems, which remove a large portion of the particulate matter entrained in the intake airflow prior to delivery into the engine's compressor section. An IPS system may remove particulate matter from the intake airflow by guiding the airflow along a flow path having a bowed or arced cross-sectional geometry such that particulate debris entrained in the airflow is directed radially outward from the engine centerline and into a particulate trap or chamber (e.g., a scroll) feeding into a dedicated IPS scavenge flow passage. The airflow through the IPS scavenge flow passage may thus contain a high concentration of particulate matter when the turboshaft engine is operated in a desert environment or other environment containing large amounts of airborne particulate debris. The IPS scavenge flow passage directs the debris-laden airflow around the other sections of the turboshaft engine before discharging the airflow overboard. A fan commonly referred to as “IPS blower” is typically positioned in the IPS scavenge flow passage to help urge the debris-laden airflow through the scavenge flow passage. An efficient IPS system may be capable of removing upwards of 95% of sand and other particulate matter from the intake air stream to provide the compressor section with a relatively clean source of air during engine operation. Nonetheless, further improvements in IPS-equipped turboshaft engines are still desired and are provided herein.